[LogFS] Prevent memory corruption on large deletes

Removing sufficiently large files would create aliases for a large
number of segments.  This in turn results in a large number of journal
entries and an overflow of s_je_array.

Cheap fix is to add a BUG_ON, turning memory corruption into something
annoying, but less dangerous.  Real fix is to count the number of
affected segments and prevent the problem completely.

Signed-off-by: Joern Engel <joern@logfs.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h
index 97195b9e93a..c9929eed80b 100644
--- a/fs/logfs/logfs.h
+++ b/fs/logfs/logfs.h
@@ -257,10 +257,14 @@ struct logfs_shadow {
  * struct shadow_tree
  * @new:                        shadows where old_ofs==0, indexed by new_ofs
  * @old:                        shadows where old_ofs!=0, indexed by old_ofs
+ * @segment_map:                bitfield of segments containing shadows
+ * @no_shadowed_segment:        number of segments containing shadows
  */
 struct shadow_tree {
         struct btree_head64 new;
         struct btree_head64 old;
+        struct btree_head32 segment_map;
+        int no_shadowed_segments;
 };
 
 struct object_alias_item {
@@ -311,6 +315,8 @@ struct logfs_block_ops {
                         write_alias_t *write_one_alias);
 };
 
+#define MAX_JOURNAL_ENTRIES 256
+
 struct logfs_super {
         struct mtd_info *s_mtd;                 /* underlying device */
         struct block_device *s_bdev;            /* underlying device */
@@ -377,7 +383,7 @@ struct logfs_super {
         u32      s_journal_ec[LOGFS_JOURNAL_SEGS]; /* journal erasecounts */
         u64      s_last_version;
         struct logfs_area *s_journal_area;      /* open journal segment */
-        __be64  s_je_array[64];
+        __be64  s_je_array[MAX_JOURNAL_ENTRIES];
         int     s_no_je;
 
         int      s_sum_index;                   /* for the 12 summaries */